The present invention is related to controlling a vibrator in a mobile phone, and more specifically to use of an accelerometer to control vibrator performance.
Mobile phones generally have a means of informing the user to incoming calls via silent alerting, e.g., vibrating. This is helpful in instances where an alerting sound is inappropriate or where an alerting sound is not adequate. Thus, tactile sensation can be used to make the mobile user aware of calls or other events, such as alarms, calendar reminders, etc.
Many mobile phones use eccentric mass vibrator motors for silent alerting. Eccentric mass vibrator motors tend to be driven at a single direct current (DC) voltage in mobile phone handsets. This voltage is one of the main factors that determines the vibrator motor's rotational speed. Internal variation in the vibrator may cause the speed of one motor (at the phone's drive voltage) to rotate at a different speed than another vibrator from the same manufacturer. In addition, as eccentric mass vibrators are used they wear which causes the motors to speed up beyond their original functional speed.
Humans are sensitive to different frequency ranges of vibration. Acceleration increases as rotational speed increases. However, beyond a certain rotational speed, the human perception of vibration begins to diminish. Thus, if a target rotational speed can be identified for a given vibrator/phone implementation such that this speed maximizes tactile sensation, it would be optimum if the vibrator motor always functioned at this rotational speed.